As the increase of the number of foreign students studying in Japan, various problems have increased which must be solved. One of them is concerned with their listening ability of Japanese in lecture rooms. This study was designed to investigate the listening ability of non-native language and propose a guideline for giving lectures so that foreign students can easily understand the lecture.Ten Japanese short sentences recorded from TV or radio programs were presented to subjects under the presence of babble noise, the sound level of which was systematically varied. Seventeen Japanese and thirty-two foreign students were tested individually and asked to write the sentence they heard.The results suggested ; (1) When there are unknown terms or unclear portions in sentences, subjects try to guess them from the context. (2) Knowledge concerning the language contributes to the guess of unclear portions. Unknown terms must be guessed phonemecally, which is a very difficult task. (3) Even though foreign students have high listening ability, they feel difficult to listen to Japanese under deteriorated conditions. (4) When key words are recognized, it is easy to understand sentences.The following guidelines were suggested for giving lectures to foreign students : (1)Use of visual aids such as overhead projectors as well as audio aids. (2)Writing on blackboard, at least keywords. (3)Speaking slowly and clearly. (4)Repeating important points. (5)Use of simple sentence structures and adding useful information to understand the context. (6)Quiet surroundings, especially forbidding private talk during lectures.